Control system for a plug-in hybrid vehicle

ABSTRACT

A control system for a plug-in hybrid vehicle includes a drive system including a starter motor, a transverse engine, and a motor/generator, and a power supply system including a high voltage battery, a capacitor, and a hybrid control module that controls charging and discharging of the capacitor. In the control system for an FF plug-in hybrid vehicle in which an external charging of the high-power battery is available, the hybrid control module starts the starter, performs mode selection control and charge/discharge control, maintains a capacitor voltage at or below a deterioration free voltage when the CS mode is selected during ignition on, and recharges the capacitor to a starter start-up permission voltage that allows the starter to start when a pre-forecast of the reverse transition from the CS mode to the CD mode is established.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National stage application of International Application No. PCT/JP2014/058470, filed Mar. 26, 2014, which claims priority based on Japanese Patent Application No. 2013-112749, filed in the Japan Patent Office on May 29, 2013, the contents of each of which is hereby incorporated herein by reference.

BACKGROUND

Field of the Invention

The present invention relates to a control system for a plug-in hybrid vehicle with a starter motor having a capacitor as power supply in which charging of a high voltage or power battery is enabled by external charging.

Background Information

Conventionally, a power storage device is known in which the voltage of the power storage device is controlled between a preset lower limit voltage and a preset holding or sustaining voltage, when the vehicle is not in use. The storage device is configured to be fully charged when the vehicle recognizes the driver through a vehicle driver authentication mechanism (for example, see JP 2008-141855 A).

SUMMARY

However, in the conventional device, when the driver turns on an ignition switch after getting in the vehicle, the storage device will be fully charged based on the recognition of the driver. Thus, although an engine start-up using the starter motor is ensured when the ignition is turned on, the storage device is maintained in full charge state. Therefore, a problem arises that deterioration of the power storage device proceeds due to an increase in the internal resistance of power storage device.

The present invention was made in consideration of the above problem and aims to provide a control system for a plug-in hybrid vehicle that can achieve suppression of the deterioration progress of the capacitor when the ignition is on, while being able to shorten the time until a starter start-up permission at the time of reverse transition from the CS mode to the DC mode.

In order to achieve the above object, the present invention has a starter motor, an engine, and a motor/generator in the driving system. As power supply system, a high voltage battery for power supply of the motor/generator, a capacitor for power supply of the starter motor, and a capacitor charge and discharge control unit for controlling charging and discharging of the capacitor are provided. In a control system for the plug-in hybrid vehicle in which external charging of the high voltage battery is available, an engine start control unit and a running mode selection control unit are provided. The engine start control unit is configured to crank the engine for starter start-up using the starter motor powered by the capacitor. The running mode selection control unit is configured to basically select, when a charge capacity of the high voltage battery is at or above a threshold, a CD mode for performing an EV running by consuming or depleting the power of the high voltage battery while selecting a CS mode for performing a HEV running so as to sustain the charge capacity of the high voltage battery. The reverse transition prediction or pre-forecast unit predicts a reverse transition from the CS mode to the CD mode.

The capacitor charge and discharge control unit is configured to maintain or sustain a capacitor voltage at or below a deterioration free voltage at which deterioration does not proceed when the CS mode is selected during ignition on, while recharging the capacitor at or above the starter start-up permission voltage once the reverse prediction from the CS mode to the CD mode has been established.

Therefore, during ignition on, when the CD mode is selected by the capacitor charge and discharge control unit, the capacitor voltage is maintained by the capacitor charge and discharge control unit at or below the deterioration free voltage. In addition, once the reverse prediction from the CS mode to the CD mode is established, the capacitor is recharged to and above the starter start-up permission voltage.

In other words, the engine start in the CD mode is performed basically by the starter start-up while the engine start in the CS mode is performed basically by an M/G start using the motor/generator. That is, during selection of CS mode, it is not necessary to elevate the capacitor voltage for preparation of the starter start-up. On the other hand, while the CD mode is being selected, it is necessary to prepare for the starter start-up. Thus, when the CD mode is selected, the capacitor voltage is maintained at or below the deterioration free voltage. Further, at the time of reverse transition from the CS mode to the CD mode, instead of being responsive to completion of the reverse transition to the CD mode, once the reverse transition prediction has been established, recharging to the starter start-up permission voltage or more will be carried out. Consequently, when the ignition is on, while suppressing the deterioration progress of the capacitor, it is possible to shorten the time required until the starter start-up permission at the time of reverse transition from the CS mode to the CD mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of this original disclosure.

FIG. 1 is an overall system diagram showing an FF plug-in hybrid vehicle to which the control system of a first embodiment is applied;

FIG. 2 is a power supply circuit diagram showing a power supply system arrangement with focus on a starter power supply source of the FF plug-in hybrid vehicle to which the control system of the first embodiment is applied;

FIG. 3 is a block diagram showing a control system configuration of the FF plug-in hybrid vehicle to which the control system of the first embodiment is applied; and

FIG. 4 is a flowchart showing a flow of a capacitor charge and discharge control process executed by a hybrid control module of the first embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Below, the best mode for implementing the control system of the plug-in hybrid vehicle according to the present invention will be described based on a first embodiment shown in the drawings.

First Embodiment

First, a description is given of the configuration. The configuration of the FF plug-in hybrid vehicle employing the control system of the first embodiment (an example of a plug-in hybrid vehicle) is described separately in a “Drive System Configuration”, “Power Supply System Configuration”, “Control System Configuration”, and “Detailed Configuration of Capacitor Charge and Discharge Control”.

Drive System Configuration

FIG. 1 is an overall system diagram showing an FF plug-in hybrid vehicle. Below, a description is given of a drive system configuration of the FF plug-in hybrid vehicle.

As shown in FIG. 1, as the drive system, a starter motor 1 (abbreviated as “M”), a transverse engine (abbreviated as “ICE”), a first clutch 3 (abbreviated as “CL1”), a motor/generator 4 (abbreviated as “M/G”), a second clutch 5 (abbreviated as “CL2”), and a belt-type continuously variable transmission (abbreviated as “CVT”) are provided. An output axis of the belt-type CVT 6 is drivingly connected to left and right front wheels 10R, 10L via a final reduction gear train 7, a differential gear 8, and the left and right drive shafts 9R, 9L. Note that the left and right rear wheels 11R, 11L are configured as driven wheels.

The starter motor 1 has a gear meshing with an engine starting gear provided on the crankshaft of the engine 2 and is powered by a capacitor 23 to be described below and forms a cranking motor for driving or rotating the crankshaft when the engine is started.

The transverse engine 2 is an engine which is arranged in the front room with the crankshaft direction in the vehicle width direction, and has an electric water pump 12, a crank shaft rotation sensor 13 for detecting the reverse rotation of the engine 2 of the transverse engine 2.

The first clutch 3 is a hydraulic dry, multi-plate friction clutch interposed between the transverse engine 2 and the motor/generator 4, which is subject to selective control by a first clutch oil pressure to complete engagement/slip-engagement/release.

The motor/generator 4 is a permanent magnet synchronous motor of three-phase alternating current type connected to the transverse engine 2 via the first clutch 3. The motor/generator 4 is driven by a power supply of the high voltage battery 21 to be described below. The starter coil of the motor/generator is connected via an AC harness to an inverter 26, which converts a direct current to a three-phase current during a driving operation while converting the three phase current to direct current during regeneration.

The second clutch 5 is a hydraulic wet-type multi-plate friction clutch interposed between the motor/generator 4 and the left and right front wheels representing driving wheels, and is subject to selective control by a second clutch hydraulic pressure to the full engagement/slip-engagement/release. The second clutch 5 makes use of a forward clutch 5 a and a reverse brake 5 b provided as a forward-reverse switching mechanism. That is, during forward traveling, the forward clutch 5 a acts as the second clutch 5, while, during backward traveling, the reverse brake 5 b serves as the second clutch 5.

The belt-type continuously variable transmission 6 is a transmission for obtaining a stepless or continuous speed change ratio by changing the winding diameter of the belt by shift hydraulic pressures to the primary fluid chamber and the secondary fluid chamber. The belt-type continuously variable transmission 6 includes a main oil pump 14 (mechanical drive), a sub oil pump 15 (motor driven), a control valve unit (not shown) that produces a first clutch hydraulic pressure and a shift hydraulic pressure using as a source pressure a line pressure that is obtained by pressure regulating the pump discharge pressure.

The first clutch 3, the motor/generator 4, and the second clutch 5 constitutes a one-motor-two-clutch drive system which operates as main drive modes according to the drive system in “EV mode”, and “HEV mode”. The “EV mode” represents an electric vehicle mode in which the motor/generator only is provided as the driving source with the first clutch 3 released and the second clutch engaged. Travelling in the “EV mode” is referred to as the “EV running”. The “HEV mode” represents a hybrid vehicle mode in which the transverse engine 2 and the motor/generator 4 act as power source with both clutches 3, 5 engaged. Travelling in the “HEV mode” is referred to as “HEV running”.

The motor/generator 4 is equipped with a regenerative cooperative brake unit 16 which controls the total braking torque during braking operation basically in response to a regenerative operation during braking operation. The regenerative cooperative brake unit 16 includes a brake pedal, an electric booster, and a master cylinder. The electric booster carries out a coordinated control of regenerative part/hydraulic part allocation such that, during braking operation, the amount that is obtained by subtracting from a required braking force represented by a brake pedal operation amount an available regenerating braking force will be borne by the hydraulic braking force.

Power Supply System Configuration

FIG. 1 is an overall system diagram showing an FF plug-in hybrid vehicle, and FIG. 2 is a power supply circuit diagram with focus on the starter power supply. Below, with reference to FIGS. 1 and 2, a description is given of the power supply system configuration for the FF plug-in hybrid vehicle.

As the power supply system, as shown in FIG. 1, a high voltage battery 21 is a motor/generator power, and a 12V battery 22 is a 12V system load power, and a capacitor 23 is a starter power supply, respectively.

The high voltage battery 21 is a rechargeable or secondary battery mounted as a power source of the motor/generator 4, and uses, for example, lithium ion battery. One or more of cell modules formed by laminating a plurality of cells is stored within a battery case. A junction box is accommodated in the high voltage battery 21, which aggregates relay circuits for supply/cutoff/distribution of high power. Further, a battery temperature adjustment unit 24 for air-conditioning function and lithium battery controller 86 for monitoring the battery charge capacity (battery state of charge; battery SOC) and the battery temperature are attached.

The high voltage battery 21 and the motor/generator 4 are connected through a DC harness 25, an inverter 26, and an AC harness 27. A junction box 28 which aggregates relay circuits of the supply/cutoff/distribution for high voltage is accommodated in the inverter 26. Further, the air-conditioning circuit 29, an electric air compressor 30, and a motor controller 83 to perform a power running/regenerative control are attached. In other words, the inverter 26 converts the direct current from the DC wiring harness into a three phase alternating current to the AC wiring harness 27 when the inverter 26 drives the motor/generator 4 due to discharge of the high voltage battery 21 during a driving mode. When the high voltage battery 21 is charged during a regenerative mode by power of the motor/generator 4, the three phase AC from the AC wiring harness 27 is converted into the direct current to the DC wiring harness 25.

In addition to a rapid external charging port 32 connected to the high voltage battery 21 through a DC harness 31, a normal external charging port 35 is connected to the high voltage battery 21 via a DC branch harness 25′, a charger 33 and the AC harness 34. The charger 33 functions to a voltage conversion and AC/DC conversion, When rapid external charging, for example, an external charging is performed by connecting a connector plug of a charging station installed in the road or the like to the rapid external charging port 32 (rapid external charging). During the normal external charging, for example, a connector plug from the household power supply is connected to the normal external charging port 35 for external charge (normal external charging).

The 12V battery 22 is a rechargeable secondary battery mounted as a power source of 12V system load 36 representing the other auxiliary equipment except the starter motor 1. For example, a lead battery is used which is generally mounted in the engine vehicle. The high voltage battery 21 and the 12V battery 22 are connected via DC branch harness 25″, a DC/DC converter 37, and a battery harness 38. The DC/DC converter 37 is intended to convert the several hundred volts voltage from the high voltage battery 21 to 12V. By controlling the DC/DC converter by the hybrid control module 81, the charge capacity of the 12V battery is configured to be managed.

The capacitor 23 is a storage device that is mounted as a dedicated power supply of the starter motor 1. A capacitor called as an electric double layer capacitor (eDLC: electric Double Layer Capacitor) is used, which has a large capacitance and excellent characteristics in quick charging and discharging performance. As shown in FIG. 2, the auxiliary load power supply system 39 and the capacitor 23 are connected via a battery branch harness 38′ provided with a fuse 40 and a capacitor charging circuit 41. The capacitor 23 and the starter motor 1 are connected via a capacitor harness 42, a resistor 43 and a relay switch 44. In addition, a DLC unit 45 is formed by the capacitor 23 and the capacitor charging circuit 41 while a starter unit 46 is formed by the starter motor 1, the relay switch 44, and the like. Below, a description of the detailed configuration of the DLC unit 45 and the starter unit 46 is given below.

As shown in FIG. 2, the DCL unit 45 includes the capacitor 23, a capacitor charging circuit 41, a self-discharge switch 47, a forced discharge switch 48, a cell voltage monitor 49 (the capacitor voltage detecting unit), and a capacitor temperature sensor 50.

The capacitor 23 is formed by connecting a plurality of DLC cells in series/parallel. The self-discharge switch 47, the forced discharge switch 48, and the capacitor temperature sensor 50 are disposed on both ends of the plurality of DLC cells in parallel. Further, the cell voltage monitor 49 is provided parallel to each of DLC cells so as to detect a cell voltage (=capacitor capacity) of each cell of the plurality of DLC cells.

The capacitor charging circuit 41 is constituted by a DC/DC converter circuit integrating semiconductor switching relays (combination circuit of switching elements, choke coils, capacitors, and a diode). The capacitor charging circuit 41 includes a semiconductor relay 51 and a DC/DC converter 52 controlled by the hybrid control module 81. The semiconductor relay 51 is a non-contact relay with light semiconductor switching elements, for example, as shown schematically in the lower left portion in FIG. 2, called as a photo-coupler for transmitting optical signals in the space of the insulated input and output. The semiconductor relay 51 has a switching function to connect or disconnect the capacitor 23 to or from the auxiliary load power supply system 38. The DC/DC converter 52 is configured to subdivide a DC input into pulse current by the switching element and connect these to obtain the direct current output of required voltage. Thus the DC/DC converter includes the function of converting the 12V direct current to the 13.5 V direct current as well as switching the capacitor charge current.

The starter unit 46 includes a starter motor 1, a relay switch 44, an electromagnetic actuator 53, and a pinion shifting mechanism 54.

The electromagnetic actuator 53, by an electromagnetic force generated by energizing the two coils 55 and 56 causes the pinion 57 to a position meshing with the ring gear 58 in addition to turning the relay switch 44 on. When cutting off the current, in addition to turning off the relay switch 44, the pinion 57 will be shifted to a position released from meshing with the ring gear 58. Note that the ring gear 58 is mounted to a crankshaft of the transverse engine 2. The auxiliary load power supply system 39 and two coils 55, 56 are connected via a battery branch harness 38″ provided with a starter cutoff relay 59, a HEV/IS/relay 60, and a starter relay 61. The energization/shut-off of the starter cutoff relay 59 is carried out by a body control module 87. The energization/shut-off the HEV/IS/relay 60 is made by the hybrid control module 81. The energization/shut-off of the starter relay 61 is made by an under-hood switching module 88. Note that, at a crossing position of the battery branch harness 38″, a voltage sensor 62 for diagnosing the relay is provided.

The pinion shifting mechanism 54 includes a pinion 57 which is axially moveable relative to the motor shaft of the starter motor 1 and a shift lever connected at its one end to an electromagnetic actuator 53 and fitted at the other end into the shift groove of the pinion 57.

Control System Configuration

FIG. 1 shows the overall system of the FF plug-in hybrid vehicle. FIG. 2 shows the power system configuration around the starter power supply, FIG. 3 shows a control system configuration. Hereinafter, based on FIGS. 1 to 3, illustrating a control system configuration of the FF plug-in hybrid vehicle.

As shown in FIGS. 1 to 3, as the control system, the hybrid control module 81 (abbreviated as “HCM”) is provided as an integrated control unit that controls appropriately the energy consumed by the overall vehicle. An engine control module 82 (abbreviated as “ECM), the motor controller 83 (abbreviated as “MC”), a CVT control unit 84 (abbreviated as “CVTCU”) are provided as control units connected to the hybrid control module 81. Further, a data communication module 85 (abbreviated as “DCM”), a lithium battery controller 86 (abbreviated as “LBC”) are provided. In addition, the body control module 87 (abbreviated as “BCM”) and an under-hood switching module 88 (abbreviated as “USM”) are provided. These control units are connected so as to be bi-directionally communicative through a CAN communication line 90 (CAN is an abbreviation of “Controller Area Network”) except for a LIN communication line 89 (LIN: abbreviation for Local Interconnect Network) through which the hybrid control module 81 and the DCL unit 45 are connected each other.

The hybrid control module 81 executes various controls based on input information from each control unit, ignition switch 91, accelerator pedal opening sensor 92, a vehicle speed sensor and the like. Among them, the control that is intended to drive a FF plug-in hybrid vehicle for which an external charging is available at a high fuel consumption efficiency is referred to as the selection control of the running mode (“CD mode” and “CS mode”) based on a battery SOC of the high voltage battery 21 (Running Mode Selection Control Unit).

During the “CD mode (Charge Depleting mode)”, in principle, a priority is placed on an EV mode in which power of the high voltage battery is consumed, and the “CD mode” is selected during a period in which the battery SOC decreases from the full SOC to a predetermined SOC. However, in a high load running so that the driving force would be insufficient in EV running, the HEV running mode is performed exceptionally. Basically, the starting operation of the transverse engine 2 during the “CD mode” being selected, start by the starter motor 1 (starter start-up) is a basic operation. The start by the motor/generator 4 (M/G start) is thus held exceptional.

The “CS mode (Charge Sustain mode)” refers to a mode in which, in principle, a priority is placed on the HEV running to maintain the power of the high voltage battery 21, and is selected as the battery SOC of the high voltage battery 21 is below the preset SOC. That is, when the battery SOC of the high voltage battery 21 is required to be sustained or maintained in a predetermined range, the HEV running is carried out by an engine power to generate the motor/generator 4. Note that the predetermined mode switching threshold, i.e. the preset SOC is set such that between a value from the CD mode to the CS mode and a value from the CS mode to the CD mode a hysteresis is provided.

The hybrid control module 81, in addition to the selection control between the “CD mode” and “CS mode”, performs an engine start-up control by the starter motor 1, a charging control to charge the capacitor 23, and the discharge control from the capacitor 23.

Also, starter related controls such as below will be carried out.

-   (A) Time reduction control from starting the engine until the     starter start-up permission. -   (B) Time reduction control from the ignition on until the starter     start-up permission. -   (C) Deterioration progress suppression control of the capacitor 23     (FIRST EMBODIMENT). -   (D) High temperature/low temperature countermeasure control of the     capacitor 23. -   (E) Voltage sag prevention control of the vehicle auxiliary     equipment.

The engine control module 82 performs a fuel injection control, an ignition control, a fuel-cut control, etc. of the transverse engine 2. The motor controller 83 performs a power driving control and regenerative control of the motor generator 4 by the inverter 26. The CVT control unit 84 performs an engagement pressure control of the first clutch 3, an engagement pressure control of the second clutch 5, a shifting hydraulic pressure control of the belt-type continuously variable transmission 6, etc. The data communication module 85, in response to remote operation of a switch of a portable remote control key and the communication being established between the portable remote control key, performs, for example, control of the locking/unlocking of a charge port lid and/or a connector locking mechanism. The lithium battery controller 86 manages a battery SOC and a battery temperature. The body control module 87 controls energization/de-energization of a starter cutoff relay 59. Finally, the under-hood switching module 87 performs energization/de-energization of a starter relay 61 incorporated therein based on a range select signal from an inhibitor switch 94.

Detailed Configuration of Capacitor Charge and Discharge Control

FIG. 4 shows a capacitor charge and discharge control processing flow executed by the hybrid control module 81 (capacitor charge and discharge control unit). Below, a description is given of each step representing a capacitor charging and discharging control processing configuration.

In step S1, it is determined whether or not the ignition switch 91 is on. If Yes (ignition on), control proceeds to step S2, while, if NO (ignition off), control repeats the determination of step S1.

In step S2, subsequent to the determination in step S1 that ignition on, it is determined whether or not the running mode selected by the running mode selection control is the “CS mode”.

If Yes (CS mode being selected), process proceeds to step S5, while, if No (CD mode being selected), process proceeds to step S3.

In step S2, subsequent to the determination in step S2 that the CD mode is selected, or, capacitor recharging in step S3, it is determined whether or not the capacitor voltage is equal to the starter start-up permission or enabling voltage or above. If Yes (capacitor voltage≧starter start-up permission voltage a), control proceeds to End, while in the case of No (capacitor voltage<starter start-up permission voltage a), control proceeds to step S4.

Here, “the starter start-up permission or enabling voltage a” is set to about 12.5V, for example, at which duration of the starter start-up falls within a target time, when the capacitor 23 exhibits the capacitor voltage of 13.5 V at fully charged state in the first embodiment, the starter start-up permission or enabling voltage a.

In step S4, subsequent to the determination in step S3 that the capacitor voltage is less than the starter start-up permission voltage a, recharging of the capacitor 23 is performed and control returns to step S3.

In case of recharging of the capacitor 23, as a charging current, normal current 1 (e.g., 15A) is selected for applying to the capacitor 23, that may suppress capacitor degradation.

In step S5, subsequent to the determination in Step S2 that the CS mode is being selected, it is determined whether or not the capacitor voltage is equal to or less than a voltage b at which degradation or deterioration would not proceed. If Yes (capacitor voltage≦voltage b), control proceeds to step S8, whereas, in the case of No (capacitor voltage>Voltage b), control proceeds to step S6.

Here, the “voltage b at which deterioration would not proceed or deterioration free voltage” is set to about 6.0 V, which may suppress deterioration progress due to increase in internal resistance in the case of the first embodiment in which the capacitor 23 exhibits 13.5 V at fully charged state.

In step S6, subsequent to the determination in step S5 or S7 that the capacitor voltage is above the voltage b, a switch 48 for forced discharge of the capacitor 23 is closed to forcibly discharge the capacitor 23, and control proceeds to step S7.

Here, the forced discharge of the capacitor is performed with the current 3 that is the normal discharge current.

In step S7, following the forced discharge of the capacitor in step S6, it is determined whether or not the capacitor voltage is at or below the deterioration free voltage b. If Yes (capacitor voltage≦voltage b), control proceeds to step S8, while, in the case of No (capacitor voltage>voltage b), control returns to step S6.

Here, as the “voltage b at which deterioration would not proceed”, the same voltage value as the step S5 is applied.

In step S8, subsequent to the determination in step S5 or step S7 that the capacitor voltage≦voltage b, it is determined whether or not the a prior prediction conditions (prior prediction 1 or 2) for transition from the “CS mode” to the “CD mode” is established. If Yes (prior prediction 1 or 2 has been established), control proceeds to step S9, while, if NO (prior condition 1 or 2 unsatisfied), control proceeds to End (reverse prior prediction unit).

Here, the prior prediction 1 refers to a condition in which the reverse transition to the “CD mode” is predicted in advance based on the increase rate of the battery SOC of the high voltage battery 21. Specifically, when the battery SOC of the high voltage battery 21 is increased, it is assumed that the current rate will be maintained, and a time from the present time is estimated that is required for crossing a mode switching threshold (for example, 25%) from the “CS mode” to the “CD mode”. Further, when the estimated time to cross the mode switching threshold falls within a preset time required to recharge the capacitor, it is determined that the reverse transition prior prediction condition is established or satisfied.

The prior prediction 2 refers to a condition to predict in advance the reverse prediction to the “CD mode” based on cruising distance during a downhill travelling. Specifically, when a downhill traveling is confirmed, based on the downhill travel range from the present time, it is estimated whether or not the mode switching threshold (for example, 25%) from the “CS mode” to the “CD mode” will be crossed. Then, crossing of the mode switching threshold is predicted when continuing the downhill travelling state. Thus, the prior prediction of the reverse transition is determined to be established. Note that the downhill determination is estimated based on longitudinal acceleration information from the longitudinal acceleration sensor, while the downhill travel range may be acquired based on GPS information indicating the host vehicle position and road information.

In step S9, subsequent to the determination in step S8 that the prior prediction 1 or 2 is established, or, subsequent to the determination in step S10 that the capacitor voltage<starter start-up permission voltage a, the capacitor 23 is recharged, and control returns to step S3.

In case of recharging of the capacitor 23, the charge current 2 (for example, 20A) is selected for recharging the capacitor 23, which is higher than current 1 (for example, 15A).

In step S10, subsequent to the capacitor recharge in step S9, it is determined whether the capacitor voltage is at or above the starter start-up permission voltage a. If YES (capacitor voltage≧starter start-up permission voltage a), process proceeds to End. If No (capacitor voltage<starter start-up permission voltage a), process returns to step S9. Here, the “starter start-up permission voltage a” is set in a similar manner as step S3.

Now, a description is given of the operation.

The operation in the control unit of the FF plug-in hybrid vehicle of the first embodiment, description is given in Characteristic Operation by Capacitor Power Supply Circuit Configuration, Charge and Discharge Operation of Capacitor Power Supply, and Capacitor Charge and Discharge Control Operation during Ignition ON, separately.

Characteristic Operation by Capacitor Power Supply Circuit Configuration

For example, in the idle stop vehicles, in the case where the power supply of the starter motor is set to a 12V battery, the power supply circuitry will be configured to be the capacitor power supply circuit configuration of the first embodiment with the DLC unit 45 and the fuse 40 excluded, which is now referred to as Comparative Example.

In this Comparative Example, a single 12V battery is commonly shared by the starter motor and the power source of the vehicle auxiliary equipment. Thus, when the power requirements is high for the vehicle auxiliary equipment, in response to an engine start-up by the starter motor, due to shortage of supply power, at the instant of the engine starting, an instantaneous voltage drop occurs with which the voltage of the vehicle auxiliary equipment abruptly falls.

In contrast, in the first embodiment, the auxiliary load power supply system 39 is formed by connecting the high voltage battery 21 and the 12V battery 22 via the DC/DC converter 37. The DLC unit 45 is configured to include the capacitor charging circuit 41 that is connected by branching from the DC/DC converter 37, and the capacitor connected to the capacitor charging circuit 41. Further, the capacitor power supply circuit is formed by a semiconductor relay 51 as a switch incorporated in the capacity charge circuit 41 between the auxiliary load power supply system 39 and the DLC unit 45.

Through this configuration, while charging the 12V battery 22 and the capacitor 23 by the power from the high voltage battery 21, the 12V battery 22 supplies the necessary power to the 12V system load 36 of the vehicle auxiliary equipment, and the capacitor 23 supplies the necessary power to the starter motor 1. That is, the power supply is not shared between the starter motor 1 and the 12V system load 36. Further, the two power supplies, i.e. the 12V battery 22 and the capacitor 23 are subjected to charge back up by the high voltage battery 21.

Further, without modifying the power supply circuit configuration of the idle stop vehicle of Comparative Example, by adding the DLC unit 45 (capacitor charging circuit 41+capacitor 23), the capacitor power supply circuit may be configured. Thus, since the DLC unit 45 may be added in a similar manner as addition of the auxiliary equipment, it is not necessary for the control of the high voltage battery 21 and the DC/DC converter 37 to be modified from the control of Comparative Example.

Furthermore, when the charge and discharge balance of the auxiliary load power supply system 39 is likely to collapse, the DLC unit 45 (capacitor charging circuit 41+capacitor 23) is capable of controlling the charging current, and may be separated from the auxiliary load power supply system 39 by the semiconductor relay 51 representing a switch. Therefore, by keeping open the semiconductor relay 51 at the time of starter start-up, it is possible to prevent the voltage of the vehicle auxiliary equipment from being decreased suddenly. In addition, there is no need to change the converter capacity of the DC/DC converter 37 and the battery capacity of the 12V battery 22 from the converter capacity and battery capacity set in Comparative Example.

Charge and Discharge Operation of Capacitor Power Supply

With respect to the capacitor power supply circuit, a description is given of “Engine start control operation by the starter motor 1”, “Charge control operation to the capacitor 23”, and “Discharge control operation from the capacitor 23” respectively performed by the hybrid control module 81.

At the time of an engine start-up by the starter motor 1, in response to the output of the starter start-up command from the hybrid control module 81, when the HEV/IS/Relay 60 is energized, the relay switch 44 is turned on to shift the pinion 57 to a position where the pinion 57 engages with the ring gear 58. Thus, the starter start-up is performed by the starter motor 1 powered by the capacitor 23 to rotate the crankshaft of the transverse engine 2, and the HEV/IS/relay 60 is shut off after a predetermined time has elapsed of the energization. Incidentally, the starter cut-off relay 59, except when the vehicle condition for prohibiting engine start is satisfied, energization is maintained by the body control module 87. Also, the starter relay 61 built in the under-hood switching module 88 is energized only during the selection of the P range. A cut-off state is maintained at the time of selection of the D range and the like other than the P range.

Accordingly, during the engine start-up control by the starter motor 1, as a rule, while the HEV/IS/relay 60 is energized by the starter start command in the starter start-up permission conditions, the starter motor 1 is driven by using the electric power of the capacitor 23 to start up the transverse engine 2.

At the time of charging to the capacitor 23, based on the output of the charge command from the hybrid control module 81, the semiconductor relay 51 of the capacitor charging circuit 41 is closed, and a capacitor charging current is selected. Thus, by introducing the power from the high voltage battery 21 into the capacitor 23 via the DC/DC converter 37, fuse 40, semiconductor relay 51, DC/DC converter 52, a short time charging takes place in accordance with the capacitor charge current. Note that the capacitor charge current is set to current 1 (for example, 15A) as a base current. Exceptionally, the current 2 (for example, 20A) is selectable in place of the current 1. Therefore, the charge control of the capacitor 23, while the charge command is output, using the power from the high voltage battery 21, the capacitor 23 is charged with the capacitor charging current selected.

At the time of discharge from the capacitor 23, based on the output of the natural discharge command from the hybrid control module 81, the self-discharge switch 47 of the DLC unit 45 is closed to perform self-discharge from the capacitor 23. Also, based on the output of the forced discharge command from the hybrid control module 81, by closing the forced discharge switch 48 of the DLC unit 45, the forced discharge is carried out from the capacitor 23. In the case of the forced discharge, the discharge amount per unit time is set larger than that of the natural discharge.

Thus, at the time of the forced discharge control of the capacitor 23, while the forced discharge switch 48 is closed on the basis of the forced discharge command, the electric power of the capacitor 23 is converted to the resistance heat, and discharge is performed in a shorter time than the natural discharge. As the capacitor discharge current, the current 3 is set to the basic current. As an exception, the current 4 is provided greater than the current 3.

Thus, at the time of the forced discharge control of the capacitor 23, while the discharge command is being output, the high voltage battery 21 is discharged at the selected capacitor discharge current.

Capacitor Charge and Discharge Control Operation During Ignition ON

As described above, the FF plug-in hybrid vehicle that allows external charging is intended to run at a high electricity efficiency, and the running mode selection control is performed based on the battery SOC of the high voltage battery 21. In this running mode selection control, during a period in which the battery SOC of the high voltage battery 21 is being reduced from full SOC to a preset SOC (=threshold value), as a rule, a priority is placed on the EV running and the “CD mode” is selected for consuming power of the high voltage battery 21. Further, upon the battery SOC of the high voltage battery 21 being equal to a present SOC (=threshold value) or lower, as a rule, the “CS mode” is selected in which the HEV running will be prioritized. Further, the startup of the transverse engine 2 while the “CD mode” is being selected is basically performed by a start-up by the starter motor 1 (starter start-up). On the other hand, with respect to the start-up of the transverse engine 2 while the “CS mode” is being selected, start-up by the motor/generator 24 is basically performed.

Therefore, by using the running mode selection control information, which is characteristic of the plug-in hybrid vehicle, in the capacitor charge and discharge control of the first embodiment, the capacitor charge amount (=capacitor voltage) is managed during ignition on.

That is, while the “CD mode” with the basics of starter start-up is selected, without waiting for the capacitor charging time, in order to enable the starter start-up in response to the starter start-up command, it is necessary to elevate the capacitor voltage in advance. In contrast, while the “CS mode” with the basis of the M/G start-up is selected, there is no need to elevate the capacitor voltage in the preparation of the starter start-up. In addition, since the capacitor increases the internal resistance and deterioration will be accelerated with a full charge state, if not used, it is preferable to discharge the capacitor to the deterioration free voltage for extending the life.

Therefore, when the ignition on, the running mode being selected is set as the management indicator of the capacitor charging state. While the “CD mode” is selected, the starter start-up is given priority. While the “CS mode” is selected, prevention of the capacitor deterioration is given priority. Further, when the reverse transition from the “CS mode” to the “CD mode” is predicated in advance, upon the prior prediction being established, recharging is started for preparation of the starter start-up. Below, with reference with FIG. 4, the charge and discharge control operation of the capacitor is described when the ignition ON, which reflects that strategy.

First, during ignition on, when the “CD mode” is selected and the capacitor voltage is less than the starter start-up permission voltage a, in the flowchart of FIG. 4, control proceeds through step S1→step S2→step S3→step S4. When the capacitor voltage at the step S3 is determined to be at or less than the starter start-up permission voltage a, the control repeats the flow through step S3→step S4. That is, when the ignition is on with the “CD mode” selected, the capacitor voltage is maintained at or above the starter start-up permission voltage a.

On the other hand, when transition from “CD mode” to the “CS mode” takes place during ignition on, since the capacitor voltage exceeds the deterioration free voltage b at which deterioration does not proceed, in the flowchart of FIG. 4, control proceeds the flow through step S1→step S2→step S5→step S6→step S7 for charging the capacitor forcibly. Then, due to the forced discharge, when the capacitor voltage is equal to or less than voltage b, control proceeds from step S7 to step S6. As long as the relationship that capacitor voltage≦voltage b is maintained, the flow proceeds to repeat the flow through step S1→step S2→step S5→step S2→End. That is, when the ignition ON with the “CS mode” selected, the capacitor voltage is maintained at or below the voltage b at which degradation does not proceed.

Furthermore, when, during the selection of the “CS mode”, the pre-forecast 1 or pre-forecast 2 to predict in advance the reverse transition from the “CS mode” to the “CD mode” is satisfied, the process proceeds from step S8 to step S9→step S10. Then, while the capacitor voltage is determined to be less than the starter start permission voltage at a step S10, control repeats the flow to proceed through step S9→step S10. Then, when the capacitor voltage is determined to be at or above the starter start-up permission voltage a in step S10, the process goes to End. That is, when the pre-forecast 1 or pre-forecast 2 during the selection of the “CS mode” is established, control starts the recharging of the capacitor to the starter start-up permission voltage a or above to set the capacitor voltage at or above the starter start-up permission voltage a so as to be prepared for the starter start-up immediately after the reverse transition to the “CD mode”.

As described above, in the first embodiment, when the “CS mode” is selected during ignition on, the capacitor voltage is maintained to or below the deterioration free voltage at which deterioration does not proceed. Further, when the reverse transition pre-forecast from the “CS mode” to the “CD mode” is established, the capacitor is configured to be recharged to and above the starter start-up permission voltage a (steps S1 to S10 in FIG. 4).

That is, normally in order to maintain the battery SOC of the high voltage battery 21 in the “CS mode”, the reverse transition from the “CS mode” to the “CD mode” cannot occur. However, when the regenerative operation such as from high mountain in the long downhill, etc., toward the plains is continued, due to high charge amount to the high voltage battery 21, a situation may occur in which battery SOC is recovered so as to be capable of transitioning to the “CD mode”. Accompanied by the reverse transition from the “CS mode” to the “CD mode”, since the starter start-up, which is inhibited during the selection of the “CD mode”, is permitted again, it is necessary to recharge the capacitor to the starter start-up permission voltage a. However, if recharging of the capacitor 23 is carried out after completion of the “CD mode” transition, the system is not in a position to be responsive to an immediate starter start-up request. In contrast, when the capacitor 23 is recharged in advance based on pre-forecast, the time for the starter start-up permission will be shortened.

Consequently, when the ignition is on, while suppressing the deterioration of the capacitor 23, it is possible to shorten the time until the starter start-up permission at reverse transition from the “CS mode” to the “CD mode”.

In the first embodiment, when the “CD mode” is selected during ignition on, the capacitor voltage is configured to be maintained at or above the starter start-up permission voltage a (steps S2 to step S4 in FIG. 4).

That is, when selecting the “CD mode”, priority is given to the starter start-up at the capacitor voltage (at or above the starter start-up permission voltage).

Therefore, when the “CD mode” is selected during ignition on, it is possible to respond to the starter start-up request quickly.

In the first embodiment, when a transition occurs from the “CD mode” to the “CS mode” during ignition on, the capacitor is configured to be forcibly discharged from the starter start-up permission voltage a to or below the deterioration free voltage b (steps S5 to S7 in FIG. 4).

In other words, due to a great gap or divergence in the capacitor voltage between the starter start-up permission voltage and the deterioration free voltage b, it takes a long time for the capacitor voltage to drop sufficiently due to natural discharge.

In contrast, associated with the transition from the “CD mode” to the “CS mode”, when reducing the capacitor voltage form the starter start-up permission voltage a or above to the deterioration free voltage b or below, by using the forced discharge, it is possible to suppress the progress of the capacitor deterioration because of rapid decrease in the capacitor voltage to the deterioration free voltage b.

Now, a description is given of the effect.

In the control system of the FF plug-in hybrid vehicle in the first embodiment, it is possible to obtain the following effects.

(1) A control system for a plug-in hybrid vehicle (FF plug-in hybrid vehicle) having a drive system including a starter motor 1, an engine (transverse engine 2), and a motor/generator 4, and a power supply system including a high voltage battery 21 representing power supply of the motor/generator 4, a capacitor representing power supply of the starter motor 1, and a capacitor charge and discharge control unit (hybrid control module 81) that controls charging and discharging of the capacitor 23, the control system comprising:

an engine start control unit (hybrid control module 81) that cranks the engine (transverse engine 2) for starter start-up using the starter motor 1 powered by the capacitor 23,

a running mode selection unit (hybrid control module 81) that basically selects a CD mode in which an EV running is performed by consuming power of the high voltage battery 21 when the charge capacity (battery SOC) of the high voltage battery 21 is equal to a threshold value or more and that basically selects a CS mode in which a HEV running is performed by maintaining the charge capacity (battery SOC) of the high voltage battery 21 when the charge capacity (battery SOC) of the high voltage battery 21 is less than the threshold value, and

a reverse transition pre-forecast unit that predicts in advance a transition from the CS mode to the CD mode (step S8, FIG. 4), wherein the capacity charge and discharge control unit (hybrid control module 81) is configured such that, at the time of ignition on with the CS mode being selected, the capacitor voltage is maintained at or below a deterioration free voltage b at which deterioration does not proceed, and, upon the reverse transition forecast from the CS mode to the CD mode being established, the capacitor is recharged to and above the starter start-up permission voltage a (FIG. 4). Thus, during ignition on, while suppressing progress of deterioration of the capacitor 23, it is possible to shorten the time until the starter start-up permission at transition from the “CS mode” to the “CD mode”.

(2) The capacitor charge and discharge control unit (hybrid control module 81) is configured, when the CD mode is selected during ignition on, to maintain the capacitor voltage at or above the starter start-up permission voltage a (FIG. 4).

Thus, in addition to the effect (1), it is possible, when “CD mode” is selected during ignition on, it is possible to response quickly to the starter start-up request.

(3) The capacitor charge and discharge control unit (hybrid control module 81) is configured, upon transition from the CD mode to the CS mode during ignition on, to forcibly discharge the capacitor from the starter start-up permission voltage a or above to the deterioration free voltage b or below (FIG. 4).

Therefore, in addition to the effects of (1) and (2), when transferring from the “CD mode” to the “CS mode”, the capacitor voltage is quickly reduced to the deterioration free voltage or below to thereby suppress progress of the capacitor deteriorate.

(4) The reverse transition pre-forecast unit (step S8 in FIG. 4) is configured to predict in advance the transition to the CD mode based on an increase rate of the charge capacity (battery SOC) of the high voltage battery 21 (FIG. 4).

Thus, in addition to the effects of (1) to (3), through higher regeneration amount in a short time, when the charge capacity (battery SOC) of the high voltage battery 21 is increased, it is possible to predict in advance the transition to the “CD mode” accurately.

(5) The capacitor charge and discharge control unit (hybrid control module 81) is configured to pre-forecast the transition to the CS mode based on a downhill travel range during a downhill travel in the CS mode (FIG. 4).

Therefore, in addition to the effects of (1) to (3), during a downhill travel at which the regenerative operation continues over a long period of time though through a small increase rate in the charge capacity (battery SOC) of the high voltage battery 21, the transition to the “CD mode” may be predicted in advance accurately.

As described above, the control system of a plug-in hybrid vehicle has been described based on the first embodiment. With respect to the specific configurations, however, the present invention is not limited thereto. Rather, according to the claims in the appended claims, without departing from the gist of the invention, design changes and additions are acceptable.

In the first embodiment, such an example is shown in which, when the CS mode is selected during ignition on, the capacitor voltage is maintained at or below the deterioration free voltage b, and, upon the reverse transition pre-forecast from the CS mode to the CD mode being satisfied, the capacitor is recharged to the starter start-up permission voltage a. However, the capacitor charge and discharge control unit may be configured to maintain the capacitor voltage at 0V when the CS mode is selected with ignition on. Alternatively, an example is conceivable in which at the time at which the reverse transition forecast from the CS mode to the CD mode has been established, the capacitor is recharged to the full charge state.

In the first embodiment, an example is presented in which the reverse transition pre-forecast unit is configured to predict in advance the transition to the CD mode based on the increase rate of the battery SOC of the high voltage battery 21, or the downhill travel range. However, the reverse transition pre-forecast unit may be configured to predict in advance the transition to the CD mode based on the history of charge amount to the high voltage battery and the regenerative amount. In essence, the mechanism suffices that is capable of predicting in advance the transition to the CD mode during running in the CS mode.

In the first embodiment, an example is shown, in which, as the capacitor charge and discharge control unit, control of recharge and forced discharge are performed using the running mode information and the capacitor voltage information. However, as the charge and discharge control unit, another example for controlling the recharging and forced discharge may be available by using capacitance information instead of the capacitor voltage information. In other words, when assuming the charge Q, the electrostatic capacity or capacitance C, and the capacitor voltage V, the charge Q is represented by Q=C·V. Thus, when the capacitance C is constant, the charge Q is proportional to the capacitor voltage V. Therefore, by using the charge information instead of the capacitor voltage information, the equivalent controlling may be achieved.

In the first embodiment, an example is shown for using the hybrid control module 81 as the capacitor charge and discharge control unit. However, as the capacitor charge and discharge control unit, a power supply system controller provided independently may be used. Alternatively, a power supply system capacitor charge and discharge control section may be provided in a controller other than the hybrid control module.

In the first embodiment, an example is shown in which the control system according to the present invention is applied to the FF plug-in hybrid vehicle. However, the control system according to the present invention is not limited to the FF plug-in hybrid vehicle, and can also be applied to a FR plug-in hybrid vehicle or a plug-in hybrid 4WD vehicle. In short, the present invention may be applied to a plug-in hybrid vehicle with a capacitor as starting power supply, in which an external charging is available to a high voltage battery. 

The invention claimed is:
 1. A control system for a plug-in hybrid vehicle having a drive system including a starter motor, an engine, and a motor/generator, and a power supply system including a high voltage battery representing power supply of the motor/generator, a capacitor representing power supply of the starter motor, and a capacitor charge and discharge controller that controls charging and discharging of the capacitor, the control system comprising: an engine start controller configured to crank the engine for starter start-up using the starter motor powered by the capacitor, a running mode selection controller configured to select a charge depleting (CD) mode in which an electric vehicle (EV) running is performed by consuming power of the high voltage battery when a charge capacity of the high voltage battery is at or above a threshold value and configured to select a charge sustain (CS) mode in which a hybrid vehicle (HEV) running is performed by maintaining the charge capacity of the high voltage battery when the charge capacity of the high voltage battery is below the threshold value, and a reverse transition pre-forecast controller configured to predict in advance a reverse transition from the CS mode to the CD mode, wherein the capacitor charge and discharge controller is configured such that, at a time of ignition on with the CS mode being selected, a capacitor voltage is maintained at or below a deterioration free voltage at which deterioration does not proceed, and, upon the reverse transition from the CS mode to the CD mode being predicted in advance, the capacitor is recharged to and above a starter start-up permission voltage.
 2. The control system for a plug-in hybrid vehicle as claimed in claim 1, wherein the capacitor charge and discharge controller is configured, when the CD mode is selected during ignition on, to maintain the capacitor voltage at or above the starter start-up permission voltage.
 3. The control system for a plug-in hybrid vehicle as claimed in claim 1, wherein the capacitor charge and discharge controller is configured, upon transition from the CD mode to the CS mode during ignition on, to forcibly discharge the capacitor from the starter start-up permission voltage or above to the deterioration free voltage or below.
 4. The control system for a plug-in hybrid vehicle as claimed in claim 1, wherein the reverse transition pre-forecast controller is configured to predict in advance the reverse transition from the CS mode to the CD mode based on an increase rate of the charge capacity of the high voltage battery.
 5. The control system for a plug-in hybrid vehicle as claimed in claim 1, wherein the reverse transition pre-forecast controller is configured to predict in advance the reverse transition from the CS mode to the CD mode based on a downhill travel range during a downhill travel in the CS mode.
 6. The control system for a plug-in hybrid vehicle as claimed in claim 2, wherein the capacitor charge and discharge controller is configured, upon transition from the CD mode to the CS mode during ignition on, to forcibly discharge the capacitor from the starter start-up permission voltage or above to the deterioration free voltage or below.
 7. The control system for a plug-in hybrid vehicle as claimed in claim 2, wherein the reverse transition pre-forecast controller is configured to predict in advance the reverse transition from the CS mode to the CD mode based on an increase rate of the charge capacity of the high voltage battery.
 8. The control system for a plug-in hybrid vehicle as claimed in claim 3, wherein the reverse transition pre-forecast controller is configured to predict in advance the reverse transition from the CS mode to the CD mode based on an increase rate of the charge capacity of the high voltage battery.
 9. The control system for a plug-in hybrid vehicle as claimed in claim 2, wherein the reverse transition pre-forecast controller is configured to predict in advance the reverse transition from the CS mode to the CD mode based on a downhill travel range during a downhill travel in the CS mode.
 10. The control system for a plug-in hybrid vehicle as claimed in claim 3, wherein the reverse transition pre-forecast controller is configured to predict in advance the reverse transition from the CS mode to the CD mode based on a downhill travel range during a downhill travel in the CS mode. 